The present disclosure relates to methods, tools, and systems for adjusting an external fixation frame. More particularly, the present disclosure relates to methods, tools, and systems for repositioning the components of an external fixation frame according to a correction plan.
The external fixation market can be divided into two major segments: acute trauma and reconstructive. The trauma segment generally includes modular fixators having fewer components and structured for rapid application to a patient. These frames may be used for temporizing fixation and may only be on the patient for hours or days.
The reconstructive segment includes ring fixators, such as the Ilizarov frame, for example. Such frames are shown in U.S. Pat. Nos. 4,365,624, 4,615,338, 4,978,348, 5,702,389, and 5,971,984. Ring fixators may be used with a combination of pins and wires to achieve a variety of polyaxial pin/wire attachments that provide stability. They can achieve a full six degrees of freedom and can correct primary deformities without creating secondary deformities. Rotational deformities may also be treated with ring fixators. However, mastery of the techniques involved with using ring fixators, as well as the products themselves, can be a long and daunting process.
At times, it may be necessary to realign, reposition, and/or securely hold two bone elements relative to one another. For example, in the practice of medicine, bone fragments and the like are sometimes aligned, realigned, and/or repositioned to restore boney continuity and skeletal function. At times, this may be accomplished by sudden maneuver, followed by skeletal stabilization with cast, plate and screws, intramedullary devices, or external skeletal fixators.
A bone fragment can be moved, in general, from its original position as in a nonunion or malunion or from its intended position as in congenital deformities along six separate movements or degrees of freedom, a combination of three orthogonal translational axes (e.g., typical “X,” “Y” and “Z” axes) and three orthogonal rotational axes (e.g., rotation about such typical “X,” “Y” and “Z” axes).
External fixation devices may be attached to the boney skeleton with threaded and/or smooth pins and/or threaded and/or smooth and/or beaded wires. Such constructs may be referred to as orthopaedic external fixators or external skeletal fixators. External fixators may be utilized to treat acute fractures of the skeleton, soft tissue injuries, delayed union of the skeleton when bones are slow to heal, nonunion of the skeleton when bones have not healed, malunion whereby broken or fractures bones have healed in a malposition, congenital deformities whereby bones develop a malposition, and bone lengthening, widening, or twisting.
A circumferential external fixator system was disclosed by G. A. Ilizarov during the early 1950s. The Ilizarov system includes at least two rings or “halos” that encircle a patient's body member (e.g., a patient's leg), connecting rods extending between the two rings, transfixation pins that extend through the patient's boney structure, and connectors for connecting the transfixation pins to the rings. Use of the Ilizarov system to deal with angulation, translation, and rotation is disclosed in “Basic Ilizarov Techniques,” Techniques in Orthopaedics®, Vol. 5, No. 4, December 1990, pp. 55-59.
Often, orthopaedic external fixators such as Ilizarov fixators must be repositioned after their initial application. Such modification may be necessary to convert from one correctional axis to another or to convert from an initial adjustment type of fixator to a weight bearing type of fixator, some of the correctional configurations not being stable enough for weight bearing.
A “Steward platform” is a fully parallel mechanism used in flight and automotive simulators, robotic end-effectors, and other applications requiring spatial mechanisms with high structural stiffness and includes a base platform, a top platform, and six variable limbs extending between the base and top platforms. See S. V. Sreenivasan et al., “Closed-Form Direct Displacement Analysis of a 6-6 Stewart Platform,” Mech. Mach. Theory, Vol. 29, No. 6, pp. 855-864, 1994.
Taylor et al. U.S. Pat. No. 5,702,389, which entire disclosure is hereby incorporated by reference herein, relates to a fixator that can be adjusted incrementally in six axes by changing strut lengths only, without requiring joints to be unclamped, etc. This patent includes a first ring member or swash plate for attachment relative to a first bone element; a second ring member or swash plate for attachment relative to a second bone element. Six adjustable length struts having first ends movably attached to the first member and second ends movably attached to the second member are provided. The first ends of the first and second struts are joined relative to one another so that movement of the first end of one of the first and second struts will cause a corresponding movement of the first end of the other strut, with the first ends of the third and fourth struts joined relative to one another so that movement of the first end of one of the third and fourth struts will cause a corresponding movement of the first end of the other strut. The third and fourth struts and fifth and sixth struts are similarly joined. Second ends of the first and sixth struts joined relative to one another so that movement of the second end of one of the first and sixth struts will cause a corresponding movement of the second end of the other strut. Second ends of the second and third struts and fourth and fifth struts are formed in a similar manner. Thus, changing the length of the struts effects the positions of the bone segments.
As discussed above, most external fixators should be adjusted over a period of time to reposition bone segments. The adjustment of the external fixation may be implemented according to a “prescription” or correction plan. Physicians may adjust the external fixator at precise times over a period of time (e.g, on a daily basis for three weeks). Patients, however, may not desire to visit the physician's office every time an adjustment is needed. For this reason, external fixators may be adjusted by the patients themselves without the assistance of a physician. The adjustment of the external fixator should nonetheless strictly comply with the predetermined correction plan. However, patients may not adjust their own external fixator according to the correction plan for a variety of reasons. For instance, patients may not understand how to use the external fixator correctly. In addition, when the patients themselves adjust the external fixators, physicians may not even know whether patients are in fact adjusting the external fixators according to the correction plan. For the foregoing reasons, it is desirable to provide a tool, system, and/or method for helping a patient implement a correction plan in an external fixator.